1. Field of the Invention
The invention concerns an arrangement for supporting a circuit board having functional components which are located on a carrier on a projectile.
2. Discussion of the Prior Art
DE 34 01 513 C2 discloses a projectile or missile in which an electronic firing circuit is disposed in a fuse housing which is fixed to the projectile casing. In that arrangement the firing circuit is foamed into a plastic material hard foam block. Fitted into the fuse housing are flat elastic damping bodies which jointly enclose the hard foam block on all sides.
A disadvantage with the operation of embedding the circuit into the block by foaming is that the mobility of functional components which must be movable can be adversely affected. Another detrimental aspect is that, when the material foams up, mechanical stresses can occur between the functional components and the circuit board, and such stresses can possibly result in the electrical connection between the functional components and the circuit board being torn away. Similar disadvantages occur if the circuit board and the functional parts or components are cast or moulded into a block.
In order to obviate those disadvantages. DE 41 12 831 A1 discloses an arrangement for supporting functional components or parts which are arranged on a circuit board, in a carrier body, in particular in a projectile, wherein the circuit board and the functional components are disposed within an opening in the carrier body. Fitted into the opening is a shaped member which is prefabricated from a compressible plastic material and the profile of which is approximately adapted to the functional components. The shaped member is squeezed against the walls of the opening by a cover for the mouth aperture of the opening so that the functional components are held against the circuit board. That known support arrangement involves force components in a radial direction, and that, having regard to the extremely high acceleration forces which occur in the case of a projectile, can give rise to major problems in regard to operational reliability of the circuit board or the functional components provided thereon.
In consideration of those factors the object of the present invention is to provide an arrangement of the kind set forth in the opening part of this specification for operationally reliably holding the functional components under the extremely high acceleration forces which occur in the case of a projectile or missile.
It has surprisingly been found that the configuration according to the invention such that the circuit board comprises a carbon fibre-reinforced plastic material, wherein an elastic damping layer is provided between the circuit board and the carrier, and that the circuit board and the damping layer are spaced with their peripheral edges from the inside wall of the projectile, prevents high force components being built up in the radial direction, so that acceleration-induced damage to the circuit board or the functional components provided thereon is avoided in a simple fashion. In accordance with the invention this advantageous quality can be still further promoted by virtue of the fact that the carrier has a metal plate which is fixed in the projectile, bridging over the cross-section thereof, In accordance with the invention the metal carrier plate is preferably formed with a through hole.
The elastic damping layer provided between the circuit board and the metal carrier plate, and in particular the metal carrier plate itself, serve to carry the axial force components of the acceleration forces. In accordance with the invention the operational reliability of the circuit board is improved in comparison with known arrangements of the general kind set forth, in that it comprises a carbon fibre-reinforced plastic material.
It has proven to be particularly desirable for the metal carrier plate to be of a thickness which is many times greater than the thickness of the circuit board and the elastic damping layer. In that case the damping layer and the circuit board may be of thicknesses which are at least approximately matched to each other. It will be appreciated that it is also possible for the damping layer and the circuit board to be of thicknesses which are different from each other or for the damping layer to be thicker than the circuit board.
In order to eliminate radial force components not just by virtue of the provision in the metal carrier plate of a through hole which is preferably provided in a central region of the metal carrier plate, it is desirable if the circuit board and the damping layer are also formed with holes. The last-mentioned holes can be in overlapping relationship with the through hole in the metal carrier plate. In that respect, the holes in the circuit board and in the damping layer and the through hole in the metal carrier plate can be at least approximately coincident with each other. Such a configuration of the above-described kind reliably eliminates radial force components resulting from the extremely high acceleration force of a projectile or missile so that damage to the circuit board or the functional components provided thereon can be reliably excluded.
The metal carrier plate of the support arrangement according to the invention can be fixed to a projecting mounting portion or bracket which radially protrudes into the projectile. The projecting mounting portion can be in the form of a collar or shoulder which extends peripherally in the interior of the projectile.
Desirably the metal carrier plate is screwed to the above-mentioned projecting mounting portion in the axial direction of the projectile. That affords the advantage of ease of assembly.
Desirably the projecting mounting portion is dimensioned with an axial dimension which is adapted to the thickness of the metal carrier plate in order suitably to optimise mechanical strength in the axial direction.
In the case of the support arrangement according to the invention it has been found advantageous for the damping layer to comprise a cellular polyurethane elastomer (PUR). Such a polyurethane elastomer is described for example in a company prospectus from Elastogran Kunststoff-Technik GmbH, Lemforde, Germany xe2x80x9cElastogran Kunststoff-Technik, EKT 0029 -3-79 or 0027-6-81/1xe2x80x9d.